Try to understand the logic here...ItemCode like '[C-Z][L-Z]%' means ItemCode's first letter should be between { C and Z } ; Second letter should be between {L and Z }... Finally you will get the ItemCode which have first 2 letters from CL to ZZItemCode like '[1-9]%' means item code starting with 1, 2, 3, 4 .... up to 9

If you would like to check the result whether correct or not , then change the ranges and check the result..for example,where ItemCode like '[C-D][L-Z]%' should return itemcodes starting with CL, CM, CN, .... DA, DB, DC, ....up to DZ